1. Technology Field
The disclosure relates generally to an apparatus and a method for sensing a distance, particularly, the disclosure relates to a distance sensing apparatus and a method for sensing a short distance.
2. Description of the Related Art
As technology rapidly advances, electronic apparatuses having function of sensing distance have more and more varieties. It is noted that, electronic rangefinding methods include electromagnetic distance measurement (EDM) and electro-optical distance measurement (EODM). The rangefinders for EODM include infrared rangefinders, laser rangefinders, and ultrasonic sensors etc. The ultrasonic sensors and the laser rangefinders have good measuring accuracy but are expensive. The infrared rangefinders are cheaper, but the measuring accuracy of the infrared rangefinders is not as good as the ultrasonic sensors and the laser rangefinders.
In general, a conventional infrared rangefinder includes an emitter and a receiver. The emitter generates an infrared light and transmits the infrared light to an object, while the receiver receives a light reflected from the object to generate an electrical signal. Because the conventional infrared rangefinder has only one receiver and compares the electrical signal with a constant reference voltage to determine a distance between the infrared rangefinder and the object according to the compared result. In addition, the material of the object directly influences the intensity of the reflected light. If the material of the object mostly absorbs light, the intensity of the reflected light is weak, causing the infrared rangefinder to generate a weak electrical signal and further influencing the measuring accuracy. In other examples, the infrared rangefinder cannot determine the distance due to the poor comparison result of the electrical signal and the reference voltage.